This invention relates to a method for the manufacture of hydrolysis-stable molding materials, laminates, stratified materials and covers or protective layers of anionically polymerisable di- or poly-epoxy compounds or mixtures of such compounds which are of high electrical and mechanical quality.
It is known that epoxy resins, especially glycidyl ether resins, can be polymerised with tertiary amines or boron trifluoride amine complexes to form molding materials. See in this connection, for instance, E. S. Narracott in "British Plastics", vol. 26, page 120 (1953), P. P. Kushch, B. A. Komarov and B. A. Rozenberg in "Polymer Science U.S.S.R.", vol. 21, Kushchpage 1867 (1979), P. P., B. A. Komarov and B. A. Rozenberg in "Polymer Science in U.S.S.R.", vol. 24, page 335 (1982) and M. Fedtke, M. Tarnow in "Plaste and Kautschuk", vol. 30, page 70 (1983) particularly page 70, paragraph 1. Preferred catalysts, for instance, for the polymerisation of aromatic diglycidyl ethers formed from bisphenol A and bisphenol F are Mannich bases of aromatic hydrocarbons or of phenols and heterocyclic compounds such as morpholine and its derivatives. These compounds result in cross-linked polymerisates which are formed in a few hours at temperatures around 100 degrees C. The molding materials so obtained are hydrolysis-stable, but the mechanical and thermal properties which are attainable by this method are inadequate for many applications. Typically, these compositions have a bending strength of less than 100 N/mm.sup.2 and a vitrification transition range of 80 to 100 degrees C. With this kind of polymerisation, aliphatic unsaturated structure elements are produced which distinctly lower the thermal and oxidative stability of the molding materials.
It is further known that in the polymerisation of epoxy resins with tertiary aromatic amines, mechanically high-quality molding materials can be obtained. These processes suffer from the disadvantage of a low cross-linking rate. The combination of tertiary amines with Mannich bases surprisingly does not bring about an improvement. Rather, the level of the epoxy/Mannich base polymerisates is preserved. It is furthermore known that imidazole and derivatives thereof are capable of polymerising aromatic glycidyl ethers and glycidyl esters (see R. Dowbenko et al. in "Ind. Eng. Chem. Prod.", vol. 10, no. 3, page 344, 1971). However, the polymerisates formed in this process do not furnish usable molding materials.
On the other hand, molding materials obtained by anionic polymerisation of epoxy resins, as compared to molding materials of epoxy resins cross-linked by polyaddition, have the advantage of a better bond between the resin matrix and embedded fillers, fibers and the like. The same can be said of the adhesion of the resin matrix to other materials.